The instant invention relates to light-reflecting molded or extruded articles having a reflectivity high enough to enhance the efficiency of illumination sources, and to methods of making the same. More specifically, the present invention relates to light-reflecting articles made of synthetic organic polymers (“plastics”) of certain composition whose structural strength, dimensional stability and other properties make them suitable for use as light-reflecting articles such as toy items for use in conjunction with light sources. The plastic compositions and articles of the invention have a potential total reflectivity of as high as about 93 to 97 percent, which is attained without the necessity of using reflective films, metal coatings, or reflection enhancers other than the compositions disclosed herein. The enhanced light reflectivity of the instant compositions occurs over a wavelength range of from about 400 to 700 nanometers.
The plastic compositions of the present invention have particularly beneficial use in toy articles. It has long been recognized that the play value of certain toy dolls can be significantly increased by imparting phosphorescent or luminescent properties to the hair thereof. Specifically, it has been recognized that by imparting color generating, or other illuminating, properties to the hair of certain toy dolls, the dolls can be effectively incorporated into imaginary concepts and themes wherein they are capable of having imaginary dreams. More specifically, it has been found that by imparting glow-in-the-dark or fluorescent properties to the hair of certain toy dolls, the dolls can be effectively incorporated into a theme wherein they live in an imaginary dream world where toy dolls are capable of having nighttime dreams.
As a result of the recognized benefits of providing relatively thin extruded filament fibers having phosphorescent properties for use in toy doll constructions as well as in other applications, one embodiment of the present invention is directed to a relatively thin, durable, translucent and fluorescent fiber which can be effectively utilized for imitation hair strands as well as for other applications, such as for textile fibers. In this regard, it has been found that doll hair fibers made from presently available flexible and durable clear plastic polymeric materials must generally have substantially uniform cross sectional dimensions which are in the range of between approximately 0.02 in. and 0.004 inches. Further, it has generally been found that fibers of these material types must possess sufficient strengths to enable them to be mechanically rooted in the heads of toy dolls and also to enable them to withstand substantial abuse.
In contemplating the use of optical brighteners or whiteners for use in extruded or molded polymer articles for reflectivity enhancement, such whiteners must also be stable to the temperatures as high as from 310 C to 330 C, which are used in processing the optical brightener into the polymeric material (eg. polyolefin) and in extruding the polymer into fiber. Additionally, the optical brightener must be non-migrating so that it remains in the polymeric material and does not exude or leach as a surface film on the polymeric molded article or extruded fiber. Such exudation may not only give rise to a nonuniform brightness of the polymer compositions and articles, but also such leaching material readily transfers to any other surface contacted with it, making it unsuitable for manual use in a child's toy. For example, when the fiber is used as doll hair, the brightener in the fiber may be transferred to the fiber surface support when the hair is wound manually by a child, adversely affecting the quality and performance of the toy.
The instant invention provides light reflecting polymeric compositions that have naphthalene-benzoxazole fluorescent brighteners or whiteners dispersed therein. These naphthalene-benzoxazole whiteners are compounds which absorb ultraviolet light and emit fluorescent light and are exemplified by bis(alkyl substituted benzoxazolyl)naphthalene compounds. In one embodiment herein, polymeric fibers are impregnated with a benzoxazolyl naphthalene optical brightening agent which can be utilized for a variety of applications including use as imitation hair fibers for toy dolls.
It has been found that generally available optical brighteners do not exhibit the combination of absorption/emission characteristics and brightening power, heat stability, and resistance to brightener exudation to the levels desired for light reflecting molded polymer articles, particularly those used in toys products. Accordingly, there remains a need for molded or fibrous polymeric articles containing optical brighteners or whiteners to enhance light reflection, the polymeric article having improved resistance to brightener exudation and wherein the optical brightener (whitener) exhibits excellent absorption/emission characteristics, brightening power and heat stability, as these characteristics relate to toy use.